1. Field of the Invention
The present invention relates to a display device, and more particularly, to a line structure of an LOG (line on glass) method in a reflective or a transflective liquid crystal display device and a method for manufacturing the same.
2. Discussion of the Related Art
In general, an LCD module is classified into two categories according to a mounting method of a drive IC, the two categories being a chip on glass (COG) mounting method and a tape automated bonding (TAB) mounting method.
In the TAB mounting method, a tape carrier package (TCP) for the drive IC is connected to an LCD panel and a printed circuit board (PCB). In a case where the TCP is connected to the LCD panel, an anisotropic conduction film (ACF) is used instead of lead by considering particular material characteristics of a glass and a metal and by considering that a pitch corresponding to 0.2 mm or below is very sophisticated. On the other hand, in a case where the TCP is connected to the PCB, lead is used.
In the COG mounting method, the drive IC is directly mounted in gate and data regions of the LCD panel, so that an electrical signal is transmitted to the LCD panel. At this time, the anisotropic conduction film (ACF) is generally used to connect the drive IC to the LCD panel.
Meanwhile, in an LCD device according to the COG mounting method, an LOG mounting method forming a conductor on a lower glass substrate is used to apply signals to each drive IC.
A general LCD device according to the COG mounting method will be described with reference to the accompanying drawings.
FIG. 1 is a cross sectional view showing a structure of the general LCD device according to the COG mounting method.
As shown in FIG. 1, the general LCD device according to the COG mounting method includes an upper substrate 101, a lower substrate 102, a printed circuit board (PCB) substrate 103, a flexible printed circuit (FPC) 104 and a data transfer cable 105. Although the details of the upper substrate 101 are not shown, a polarizer is formed on one surface of the upper substrate 101, and a color filter and a common electrode are formed on the other surface of the upper substrate 101.
The lower substrate 102 is larger than the upper substrate 101. The polarizer is formed on one surface of the lower substrate 102, and the other surface of the lower substrate where the polarizer is not formed is opposite to the common electrode of the upper substrate 101. As shown in FIG. 1, a data line 109 of a data drive IC 107 is formed perpendicular to a gate line 108 of a gate drive IC 106. A plurality of input signals generated from a drive circuit of the PCB substrate 103 are applied to the data drive IC 107. A drive input line 110 of the data line 109 in which the input signals flow is connected to the FPC 104 and the data drive IC 107. Also, data output lines 111 of the data drive IC 107 are respectively connected to each data line 109.
A gate input signal of the drive circuit of the PCB substrate 103 is applied from the FPC 104 to the gate drive IC 106 through the drive input line 110 of the gate line. Then, the gate drive IC 106 generates a gate voltage for driving the LCD device, and outputs the gate voltage to an output terminal. At this time, the output terminal of the gate drive IC 106 is connected to each gate line 108 through gate output lines 112.
The data transfer cable 105 is formed to connect the PCB substrate 103 to the FPC 104, so that signals generated from the drive circuit of the PCB substrate 103 are applied to the data drive input line of the FPC substrate 104. That is, signals generated from the drive circuit of the PCB substrate 103 are applied to the data drive input line of the FPC 104 through the data transfer cable 105.
In the LCD device according to the present invention, a plurality of FPCs are required since a width of the FPC has to be widened to prevent a short from generating in input lines connected to an input terminal of the drive IC.
To use a small number of FPCs, it is useful to form the LCD device of the LOG method in which input lines of the data drive IC and the gate drive IC are directly formed on the lower substrate.
FIG. 2 illustrates a general LCD device according to an LOG method in which an input line is directly mounted on a substrate.
As shown in FIG. 2, the LCD device includes the PCB substrate 103, the FPC 104 having transfer lines, the lower substrate 102 and the upper substrate 101.
The lower substrate includes the input line 114 of the gate drive IC, the input line 113 of the data drive IC, a common voltage line (not shown), the gate drive IC 106, the data drive IC 107, the gate line 108 and the data line 109. In the upper substrate, a common electrode is formed. Although not shown, the common electrode is connected to the common voltage line of the lower substrate.
Referring to FIG. 2, in the general LCD device, the drive circuit of the PCB substrate 103 generates various input signals for driving the LCD device, and then the input signals are input to the transfer line of the FPC 104. Each transfer line of the FPC 104 is respectively connected to the input lines 114 of the gate drive IC 106 directly mounted to the lower substrate 102, and the input line of the data drive IC 107 directly mounted to the lower substrate 102.
The input signals applied to the input lines are input signals of the gate drive IC 106 and the data drive IC 107, and output signals of the drive ICs 106, 107 are respectively applied to each gate and data line 108, 109, thereby driving the LCD device according to signals of the gate and data lines 108, 109 applied the output signals.
FIG. 3 illustrates a cross sectional view showing a structure of an input line in the general LCD device according to the LOG method.
As shown in FIG. 3, an input line 202 is formed of the same material as the gate electrode on an insulating substrate 201, and then a gate insulating layer 203 is formed on an entire surface of the substrate 201 including the conductor 202 (input line). Then, an organic insulating material is deposited on the gate insulating layer 203 to form organic insulating layer 204, and a passivation layer 205 is formed on the organic insulating layer 204.
However, the related art LCD device and the method for manufacturing the same have the following problems.
In the circuit of the related art LCD device having a single-layered input line structure, a line resistance is higher than in the FPC, so that the drive signal is retarded, thereby generating a failure for exactly driving the LCD device.